Fig. 23
From: Within-family plasticity of nervous system architecture in Syllidae (Annelida, Errantia)
Schema of the longitudinal innervation of a segment in Syllidae. Four segmental ring neurite bundles are present per segment, of which the fourth one lies at segment boundaries and may be missing between some segments. The dorsal longitudinal neurite bundle connects segmental neurite bundle II of one segment to III, IV of the same and I and II of the next segment. It starts above the neurite bundle innervating the ventral cirrus on segmental neurite bundle II and ends in a dorsomedian position on the next segmental neurite bundle. The lateral longitudinal neurite bundle emerges underneath the neurite bundle innervating the tentacular cirrus and ends above it, connecting II to III, IV, I and II. The ventral longitudinal neurite bundle follows a straight course, interrupted by the neurite bundles forming the parapodial innervation (II), except for P. brevipes. The longitudinal neurite bundles follow a straight course in anterior segments approximately until reaching the proventricle. They then follow the course of the schema